I’m not sure if I intended it to be the case (probably not), but LaTeX picked up the braces around the address as the argument to letter. When I used this as the template for a personal letter and deleted the address, all hell broke loose.

As a follow-up to my own comment #2, I just came across an alternate way of defining a letter, using the \letter command. It formats the letter slightly differently, and it appears that you can only include one such command per document.

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A place to document tips and tricks for the various Linux, LaTeX, OCaml, and other general computer-related topics that I encounter in my daily life and a repository for supposedly amusing observations, hyperlinks, recipes, reviews, travelogues, and political opinions written when I have a spare moment (or when I don't have a spare moment, but I don't feel like working)